In clinical applications, TCA (time curve analysis) is an important measure for quantitative analysis of abnormal zone (tumor etc.) in an ultrasound image sequence. However, it is well known that in time curve analysis, the region of interest (ROI) which the observer is interested in, such as a tumor region, would vary continuously in a series of ultrasound images obtained over time, and motion tracking of ROI is one important step for obtaining reliable TCA results for the ROI (such as tumor region).
In order to enhance the precision of tracking ROI's motion, patent document 1 (Japanese Patent Application No. 2008-289623) proposed a solution in which image information (frames) before and after a specified time phase is read out from memory circuitry to obtain an intermediate imaginary frame and a small region image (ROI) is calculated. In this solution, the calculation on ROI's moving position adopts the image correlation processing such as region matching method. By means of this technical solution, ROI with low correlation may be determined as unwanted images such as noise, and luminance information of corresponding positions can be decreased.
However, the technical solution in patent document 1 did not take into account the occurrence of the inaccurate image information before and after a specified time phase. For example, in case that missing frame or periodical drastic variation of ultrasound image intensity occurs during sampling, the expected ROI may not exist in the two frames before and after the specified time phase. Even if a reference frame is obtained based on these two frames, the subsequent calculation result is not accurate and ROI motion tracking with high precision cannot be implemented, since there is no expected ROI in the reference frame. In addition, in patent document 1, the region matching method is used for the calculation of ROI's moving position. However, its region matching is implemented between only two regions obtained by the above mentioned method. In case that frame loss or large variation of image intensity occurs in the process, the differential value of moving positions is also inaccurate.